1. Field of the Invention
The present invention is in the field of metering rolls, and more particularly pertains to an anilox roll having improved wear characteristics as well as permitting high definition printing.
2. The Prior Art
It is known to provide an anilox or metering roll which comprises a cylindrical metallic core, generally plated, having formed in the periphery thereof a multiplicity of regularly spaced ink capturing cells. The objective of the anilox roll is to apply discrete increments comprising predictable quantities of ink or like fluids to a surface contacted with the roll.
It is likewise known that the results achieved are dependent upon the configuration of the dispensing cells and their concentration, the finer the cell pattern, the finer the printing possible through the use of the roll.
As an example of an advanced form of anilox roll, there may be mentioned United States Patent 3613,578 and the patents cited therein.
Since anilox rolls are exposed to corrosive fluids, it is necessary that the same be afforded a degree of protection, and typically a plating procedure wherein the cells are coated with chromium or like material is employed for such purpose.
Anilox rolls of the type hereinabove discussed are expensive to manufacture and are subject to relatively rapid wear in use, whereby their ink transfer characteristics progressively change.
It has heretofore been contemplated to apply ink with a cylindrical metal core having a ceramic coating. Such rolls, while highly wear resistant, included surface portions having random configurations whereby the ink release patterns and characteristics were unpredictable. Since such rolls failed to include the desired regularly spaced and especially shaped metering cells on their outer periphery, their utility was restricted to rough printing applications, such as corrugated boxes, wherein the reproduction of fine detail was not contemplated. Such rolls typically included relatively thick ceramic coatings, in the area of about 0.02 or 0.03" to protect the core against corrosion. In some instances a sealer was applied over the coating to define a layer which was worn away in the course of use of the roll.
More recently, in accordance with U.S. Pat. No. 4,009,658, it was proposed to provide a ceramic coated roller having regularly spaced metering cells on the outer surface thereof. In accordance with the teachings of such patent, the surface of the metallic core was first formed with a series of regularly spaced impressions or indentations of a size substantially larger than the size of the cells which were ultimately desired.
Thereafter, a ceramic coating was applied over the patterned surface to a thickness efficient to define a sealing coating, the result of such ceramic application being to provide an external ceramic surface having dispensing cells therein.
The roll of the above mentioned patent provides a practical, effective and long lived applicator roll suitable for printing processes of a far finer nature than those which might be achieved through the use of the flat or random ceramic rollers theretofore known. However, the procedure could not produce an anilox roll capable of achieving the detail and definition comparable to all metal anilox rolls, such as the roll disclosed in U.S. Pat. No. 3,613,578 referred to above. The reason for such incapacity was that the applied ceramic coating distorted the configuration of the cells in an uncontrollable manner. Also the maximum cell concentration which might be achieved was lower than that required for fine printing applications, being in the order of from about 35 to 90 cells per linear inch whereas fine anilox printing may require cell concentrations of up to 550 cells per linear inch in each direction.